Recent progress in thermal/environmental barrier coatings and their corrosion resistance

One of the important applications of yttria-stabilized zirconia (YSZ) is as a thermal barrier coating for gas turbine engines. While YSZ performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite-derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability, and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatings are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.

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Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

Homologous layered InFeO 3 (ZnO) m : new promising abradable seal coating materials

We report on the thermal properties of InFeZnO4 which belongs to a general family of homologous layered compounds with general formula InFeO3(ZnO)m (m=1, 3, 5 …). InFeZnO4 exhibits low thermal conductivity, which decreases from 2.86 W·(m·K)−1 at room temperature to 1.36 W·(m·K)−1 at 1200°C. InFeZnO4 also shows moderate thermal expansion coefficients, close to ∼11.7 × 10−6 K−1 at 1200°C, which closely match that of usual metallic substrates. Therefore, this material is very promising as thermal barrier coatings.

InFeZnO4 as Promising Thermal Barrier Coatings

In the present study, (Sm1−xDyx)2Ce2O7 solid solutions were synthesized by solid reaction at 1600 °C for 10 h in air. The phase structure, micro-morphology and thermophysical properties of (Sm1−xDyx)2Ce2O7 oxides were examined. XRD results indicated that pure (Sm1−xDyx)2Ce2O7 oxides with fluorite structure were prepared. SEM revealed that their microstructures were very dense and there were no other phases among the particles. The thermal conductivity and thermal expansion coefficient of the ceramics remarkably decreased through Dy-doping. Their thermal expansion coefficients were higher than that of YSZ, and their thermal conductivities were much lower than that of 8YSZ. Their excellent thermophysical properties imply that these solid solutions are potential materials for the ceramics layer in thermal barrier coatings.

Yuan Wei

Papers

Thermophysical properties of Sm2(Zr1−xCex)2O7 ceramics